Hairy cell leukemia has recently been found to be responsive to recombinant alpha interferon. This drug is capable of inducing complete responses in patients with this disease, but the early results suggest that this drug is incapable of curing the disease or of making all patients respond continuously. As a result, we are currently investigating the use of combining recombinant alpha interferon with 2'-deoxycoformycin, another drug recently found to have significant activity in hairy cell leukemia. This combination approach appears to be particularly attractive since small numbers of patients resistant to alpha interferon have responded to deoxycoformycin. Although very active in this disease, deoxycoformycin has significant toxicity as well. We are administering deoxycoformycin in low doses weekly for three consecutive weeks followed by one month of daily recombinant alpha interferon. By this mechanism we hope to avoid the cumulative toxicity with deoxycoformycin and yet still be able to take advantage of its rapid antileukemic effect. By interrupting dCF therapy, we hope to limit the toxicity related to this drug. However, while patients are recovering from dCF-related toxicity, continuing antileukemic therapy in the form of alpha interferon will be continued. In this way, we hope to take advantage of the beneficial aspects of deoxycoformycin and interferon while at the same time minimumizing the negative aspects of each drug. So far eight patients have been admitted to this study, and as expected all patients are showing early signs of response. Significant myelosuppression due to deoxycoformycin has been observed in all patients. Two patients of the initial eight have been admitted to receive antibotics for granulocytopenia and fever. It is too early to comment on the extent or duration of response.